INSECT BITE ALLERGIES IN CATS
Minou' is a regular cat with irregular skin. She has a tendency to over react to any insect assualting her. Her previous problems included a scabby skin due to Flea Bite Allergy, so when she came in with knobbly nose and ears, I had a fair idea that other insects were now causing her problems.
Diagnosing the problem
There are many causes of damaged ears and noses in cats, including skin cancer (especially in pink-nosed and white-eared cats, and increasingly in coloured ears also), and fungal infections (cryptococcosis), so close examination, and often biopsy of the area is necessary.
The biopsy of the bridge of Minou's nose indicated that insects were the main cause of the reaction, and most likely to be mosquitoes in fact. Up in Brisbane, one of the dermatologists did a very elegant study showing that the noses of these cats cleared up if mosquitoes were excluded from their environment. He even has an amazing photo of a mozzie sitting on the bridge of a cat's nose!
Apparently, cats don't feel the bite itself, only the reaction to the mozzie saliva an hour or so later, so they don't even try to swatt them off. Typically, the pads of the forefeet will also be inflamed, because of the way cats sit and doze with their forepaws curled up.
Managing mosquitoes
Cats are especially sensitive to many insecticidal compounds. For this reason it is not advisable to use dog or human products on your cat - the ingredient DEET (in some personal insect repellants) has caused problems for some cats. To treat the bites on the ears and nose of your cat you can use an antiseptic cream, such as Dermaclens Cream or Filta-Bac sunscreen (contains an antiseptic as well as a sunscreen). If the bites appear infected then it would be best to get an antibacterial cream from your vet.
The most effective treatment for your cat is to thwart the maurading mozzie! For mosquito prevention it is recommended to remove sources of stagnant water around the house and garden where mosquitoes might breed and change water bowls frequently, fit screens to windows, doors and other exposed areas of your house to prevent mosquitoes entering inside, and keep your cat inside in the early morning and early evening when mosquitos are most active. You can use mosquito repellants outside your house, such as mozzie zappers.
Harvest mites
Now for the scabby ears! Often the outside and inside of the ear (the pinna) has little hard area, jus like ours when a mozzie bites. If these irritations are more on the edge of the ears, rather than in the centre, it may be that grass or harvest mites are also annoying the cat. The little 'trombiculid' mites are very irritating, and quite hard to get rid of as they live in the lawn and multiply rapidly during the warm weather.
Most of them are repelled either by pyrethrin-based products or ointments applied to the ears, or by regular (every 2 weeks) applying of Frontline Spray to the ears (sadly, the Frontline Topspot won't do as it does not stay for long enough in sufficent strength to kill the mites).
Severe reactions
Left unattended, or where the cat has a really strong allergic reaction to insect bites, the nose can become very deformed, and the 'leather' on the end of the nose can ulcerate and even be destroyed. For these cats, fairly aggressive corticosteroid and antibiotic therapy is needed to get them comfortable again, as the initial irritation becomes self-perpetuating. Much better to resolve the problem while the nose and ears are only looking lumpy, rather than weeping and ulcerated!
Fortunately, most cats can tolerate most insect assaults, and perhaps their attacks on larger flying insects is only revenge!